Wikipedia
USBKill is anti-forensic software distributed via GitHub, written in Python for the BSD, Linux and OS X operating systems. It is designed to serve as a kill switch if the computer on which it is installed should fall under the control of individuals or entities the owner or operator does not wish it to. It is free software, available under the GNU General Public License.
The program's developer, who goes by the online name Hepahest0s, created it in response to the circumstances of the arrest of Silk Road founder Ross Ulbricht, during which U.S. federal agents were able to get access to incriminating evidence on his laptop without needing his cooperation by copying data from its flash drive after distracting him. It maintains a whitelist of devices allowed to connect to the computer's USB ports; if a device not on that whitelist connects, it can take actions ranging from merely returning to the lock screen to encrypting the hard drive, or even deleting all the data on it. However, it can also be used as part of a computer security regime to prevent the surreptitious installment of malware or spyware or the clandestine duplication of files, according to its creator.